Bioengineering a Single-Protein Junction

Abstract

Bioelectronics moves toward designing nanoscale electronic platforms that allow in vivo determinations. Such devices require interfacing complex biomolecular moieties as the sensing units to an electronic platform for signal transduction. Inevitably, a systematic design goes through a bottom-up understanding of the structurally related electrical signatures of the biomolecular circuit, which will ultimately lead us to tailor its electrical properties. Toward this aim, we show here the first example of bioengineered charge transport in a single-protein electrical contact. The results reveal that a single point-site mutation at the docking hydrophobic patch of a Cu-azurin causes minor structural distortion of the protein blue Cu site and a dramatic change in the charge transport regime of the single-protein contact, which goes from the classical Cu-mediated two-step transport in this system to a direct coherent tunneling. Our extensive spectroscopic studies and molecular-dynamics simulations show that the proteins' folding structures are preserved in the single-protein junction. The DFT-computed frontier orbital of the relevant protein segments suggests that the Cu center participation in each protein variant accounts for the different observed charge transport behavior. This work is a direct evidence of charge transport control in a protein backbone through external mutagenesis and a unique nanoscale platform to study structurally related biological electron transfer.

From Exhaustive Simulations to Key Principles in DNA Nanoelectronics

“…Our main finding is that quantum coherent effects are prevalent, and they play a central role in biological electron transport over the distance of few nanometers. It is interesting to explore similar questions of electron transfer through proteins [71].…”

Improving Gating Efficiency of Electron Transport through Redox‐Active Molecular Junctions with Conjugated Chains

“…[7] Among them, redox-active molecules could be converted between the oxidized and reduced states upon different electrochemical potentials, and have been widely studied to illustrate the electrochemical gating at single-molecule level, such as ferrocene, [8] pyrrolo-tetrathiafulvalene, [9] anthraquinone, [10] viologen, [11] transition metal complex [8a,12] and redox-active DNA or proteins. [13] Their conductance could switch on as the energy level of electrodes shifted to resonance with molecules. With this unique family of redox-active molecules, ongoing interest is to obtain a high on/off ratio of conductance.…”

A Solid‐State Protein Junction Serves as a Bias‐Induced Current Switch

“…[1,2] Thea bility to rationally design protein-based electrical components,r equires fundamental understanding of their charge-transport mechanism. [1,3,4] Ear-lier studies have shown that the characteristics of electronic charge transport, ETp,via protein junctions are influenced by the protein structure, [5][6][7] electrode-protein coupling, [8][9][10] and the alignment of frontier molecular orbital energies with respect to the Fermi levels (E F )o ft he electrode, [11,12] often characterized by as ingle parameter known as the energy barrier. [13] Thec ombination of protein molecular orbitals and their coupling to the electrodes dictates the transmission probability across the junction.…”